When does inflation turn into something acceptable? Most inflation is NOT good, but is there a clear line that would define acceptable inflation?

In the U.S. and most other countries we are willing to accept an inflatiion rate as high as 3% as acceptable and in some minds a good thing. After all, inflation on a small scale will NOT disrupt the economy or erode people's savings rapidly as happened in 1923 in Germany and Austria after WWI. So most economists would say anywhere from 1-3% is an acceptable rate of inflation for a country and may even suggest that it is generally good for the economy. wmw

Not really. The answer would change from country to country, and would also change in each country over different time periods. I am from India, and in our country, inflation has been at, or slightly higher than double digit for a while now, and we've been doing reasonably well. But the United States hasn't had double digit inflation for about thirty years now.
Long answer short? There isn't a clear line, and there can't be one.